Curable casting compositions having a high refractive index and high impact resistance

ABSTRACT

A high refractive index composition comprising a core resin mixture comprising a mixture of ethoxylated bisphenol A di(meth)acrylates and/or their derivatives having variable degrees of ethoxylation to provide enhanced impact resistance and refractive index.

FIELD OF THE INVENTION

The present invention relates to curable casting resin compositions thatmay be used in the formation of a variety of materials, including, butnot limited to, lenses, camera optics, prisms and video disks.

BACKGROUND OF THE INVENTION

Ophthalmic lenses produced in industry must meet certain requirementsfor their intended use. For example, as mandated by the U.S. Food andDrug Administration (FDA), ophthalmic lenses should have sufficientimpact resistance in addition to having acceptable optical properties.The performance and quality of lenses has been improved with theaddition of scratch resistant coatings, anti-reflective (AR) coatings,UV protection and lens materials with high refractive index and highAbbe value. Further, lens cosmetics have also been improved by asphericand progressive lens designs.

Many efforts in fonnulating UV curable casting resin compositions havebeen made to produce thinner lenses having a high refractive index. Byincreasing the refractive index of the lens materials, the edgethickness of minus-prescripted lenses and center thickness ofplus-prescripted lenses is reduced. Reducing edge and center thicknessesof lenses provides functional advantages such as lighter weight andbetter cosmetics. Representative examples of UV curable casting resinformulations for forming lenses are described below.

U.S. Pat. No. 4,306,780 discloses high index lens formulationscomprising three types of materials: (a) 3-70% of one or more ofethoxylated bisphenol A di(meth)acrylates, (b) 30-97% of high indexreactive diluents, and (c) 0-67% of low index methacrylate(s). Based onthe information provided in the patent disclosure, low impact resistanceand inferior thermomechanical properties are expected from the highrefractive index lenses made from these formulations because of thelarge amount of reactive diluent used in the formulations.

U.S. Pat. Nos. 5,442,022 and 5,545,828 disclose lens formulationscomprising (a) at least 50% of a monomer ormixture of monomers havingformula (A), (b) 0-50% of one or more mono- or poly-functional vinyl or(meth)acrylate comonomers, and (c) 0.5 to 15% of allyl alcohols or theirderivatives. Lenses produced from a homopolymer of formula (A) have arefractive index greater than or equal to 1.55; however, these lenseshave an inferior physical/cosmetic property in that they are very yellowin color. Further, although incorporating components (b) and (c) intothe lens formulations reduces the yellowness of the resulting lens, lensformulations comprising components (a), (b) and (c) produce lenseshaving an undesired lower refractive index. Also, the typical time forthermally curing these lens formulations is more than 20 hours. A curingtime of this length drastically reduces lens manufacturing efficiency.The formula disclosed in U.S. Pat. Nos. 5,442,022 and 5,545,828 may berepresented by: Formula A

wherein R₁, and R₂ are H or C₁-C₆alkyl; X is O, S, SO₂, CO₂, CH₂, CH═CHor C(CH₃)₂; and m+n is 0-10.

U.S. Pat. No. 5,373,033 discloses casting resin formulations with (a)5-60% of polyoxyalkylene glycol di(meth)acrylates, (b) 10-60% ofbisphenol-based monomers having the general formula (B) and a secondhigh index component to adjust the refractive index, and (c) 2.5-20% ofurethane (meth)acrylates. The impact resistance for these formulationswas not reported; however, the impact resistance is expected to beimproved due to the introduction of urethane (meth)acrylates into theformulation. The reported refractive index of the cured sample is nomore than 1.55. The formula disclosed in U.S. Patent No. 5,373,033 maybe represented by:

wherein R₁ is H, CH₃ or CH₂CH₃; R₂ is H, CH₃ or CH₂CH₃; R₃ is H, CH₃ orOH; R₄ is H, CH₃ or CH₂CH₃; X is a halogen (preferably Cl, Br or I) orhydrogen; and n is 0-8.

The lenses produced using these high index materials represented aboveby formulae (A) and (B) may have one or more of the shortcomingsmentioned above. For instance, the high index materials of formulae (A)and (B) are mixed with at least 2 other types of materials to adjustindex, viscosity and impact resistance in order to obtain lenses withreasonable overall properties. However, the impact resistance andthemomechanical properties of these lenses are expected to be inferior.Further improvement is needed to formulate high index casting resinscapable of producing much higher quality lenses by developing new highindex materials.

Steps have also been taken to impart UV protection in lenses producedfrom the aforementioned formulations. These steps are typicallyaccomplished by dipping the cured lenses in a UV tinting bath inseparate steps. However, the UV tinting process tends to introduceyellowness into the lens and increases the cost of lenses.

Thus, there is a need to formulate a low viscosity casting resinformulation that is curable in a short amount of time and produceslenses having a high refractive index and excellent impact resistance.In particular, there is a need for high impact resistance in lenseshaving a center thickness of 1 mm. That way, true thin and light highrefractive index lenses having the required impact resistance can beproduced. Further, there is a need for lenses having at least 99%inherent UVA protection up to 380 nm. Having inherent UV protectioneliminates additional UV tinting process steps and the resultingyellowness in the lens. Lastly, a casting resin composition of lowviscosity enables easier processing in the mold-filling stage andprevents flow lines and bubbles in the cured lenses.

SUMMARY OF THE INVENTION

The present invention is generally directed to a low viscosity castingresin composition that can be cured under radiation to produce highrefractive index lenses with excellent impact resistance and inherent UVprotection, even on lenses with 1 mm center thickness. By mixingethoxylated bisphenol A di(meth)acrylates of varying degrees ofethoxylation, compositions can be obtained with an enhanced balance ofimpact resistance and refractive index. Moreover, the present inventionis directed to a curable casting resin composition having a UV absorbertherein to provide more than 99% inherent UVA protection.

In one aspect, the present invention is directed to a high refractiveindex composition comprising:

a core resin mixture comprising

(i) an ethoxylated bisphenol A di(meth)acrylate having the formula (I):

wherein n and n′ independently are 0-30, R₁-R₄ independently represent Hor C-C₆ alkyl, X is O, S, SO₂, CO₂, CH₂, CH═CH, C(CH₃)₂ or a singlebond, and y₁-y₈, independently represent H, OH, halogen, mercaptan orC_(1-C) ₄ alkyl,

(ii) an ethoxylated bisphenol A di(meth)acrylate having the formula(11):

wherein m and m independently are 1-30, R₁-R₄ independently represent Hor C₁-C₆ alkyl, X is O, S, SO₂, CO₂, CH₂, CH═CH, C(CH₃)₂ or a singlebond, and y₁-y₈ independently represent H, OH, halogen, mercaptan orC₁-C₄ alkyl, and

(iii) a reactive diluent;

the mixture having greater than 70 parts by weight of the composition ofthe combined components (i) and (ii), and less than 30 parts by weightof the composition of component (iii), based on the total parts byweight of the core resin equaling 100, and n and n′ being less than mand m′ so as to provide a refractive index of greater than 1.53 and ahigh impact resistance after curing the composition.

In another aspect, the composition of the present invention comprises

(a) a core resin comprising

(i) greater than 70 parts by weight of the composition of an ethoxylatedbisphenol A di(meth)acrylate or a mixture of ethoxylated bisphenol Adi(meth)acrylates having the formula (I):

wherein n and n′ independently are 0-30, R₁-R₄ independently represent Hor C₁-C₆ alkyl, X is O, SO SO₂, CO₂, CH₂, CH═CH, C(CH₃)₂ or a singlebond, and y₁-y₈ independently represent H, OH, halogen, mercaptan orC₁-C₄ alkyl,

(ii) less than 30 parts by weight of the composition of a reactivediluent, based on the total parts by weight of the core resin equaling100; and

(b) up to 2 parts by weight of a UV absorber per 100 parts by weight ofthe core resin.

The present invention is also directed to a method of forming a curedarticle from the compositions of the present invention. The methodcomprises the steps of: (a) filling a mold with a high refractive indexcurable resin composition of the present invention; (b) curing thecomposition of step (a) by exposure to a radiation source therebyforming a cured article; (c) demolding the cured article; and (d)annealing the cured article. Preferably, the article is a lens.

DETAILED DESCRIPTION OF THE INVENTION

The present invention may be understood more readily by reference to thefollowing detailed description of particular embodiments of theinvention and the specific examples included therein.

Before the present compositions and methods are disclosed and described,it is to be understood that this invention is not limited to specificsynthetic methods or to particular formulations, as such may, of course,vary. It is also to be understood that the terminology used herein isfor the purpose of describing particular embodiments only and is notintended to be limiting.

In this specification and in the claims which follow, reference will bemade to a number of terms which shall be defined to have the followingmeanings.

The singular forms “a,” “an” and “the” include plural referents unlessthe context clearly dictates otherwise.

“High refractive index” or “high index” when used in reference to thepolymer formed from a casting resin composition means that the curedpolymer preferably has a refractive index (RI) of at least 1.53, andmore preferably of at least 1.56.

“Inherent UV protection” when used in reference to the polymer formedfrom a casting resin composition of this invention means that the curedpolymer having a UV absorber therein preferably has ultra violet (UV)blockage of 100% UVB and at least 95% and more preferably of at least99% UVA (up to 380 nm).

“Core resin” when used in reference to a curable casting resincomposition of this invention refers to a resin having the combinationof an ethoxylated bisphenol A di(meth)acrylate monomer and/or mixturesthereof and a reactive diluent.

The term “ethoxylated bisphenol A di(meth)acrylate” (referred to hereinas “the first compound and the second compound”) refers to itself aswell as its derivatives as outlined in formulae (I) and (II).

The term “(meth)acrylate” or “(meth)acrylate mixtures” when used inreference to the curable casting resin composition of this inventionrefers to an acrylate monomer wherein the monomer or monomer mixture maybe a methacrylate or acrylate.

The term “reactive diluent” refers to a radically polymerizable monomerused to reduce the concentration of the cthoxylated bisphenol Adi(meth)acrylate and/or mixtures thereof to achieve the presentlydescribed desirable and beneficial effects, especially low viscosity,high refractive index and/or better thermomechanical properties.

The amount of reactive diluent used in the core resin varies accordingto the types and amounts of ethoxylated bisphenol A di(meth)acrylateused, and is used in an amount to effect a high refractive index withoutsacrificing a high impact resistance imparted to the resulting curedsubstrate or lens.

The curable casting resin composition of this invention may be a coreresin copolymer comprising an ethoxylated bisphenol A di(meth)acrylatemonomer and a radically polymerizable reactive diluent monomer. Thiscomposition, which may be subsequently cured into a high refractiveindex lens, for example, can easily be obtained by copolymerizing anyone ethoxylated bisphenol A di(meth)acrylate monomer component and thereactive diluent monomer component, or by homopolymerizing anethoxylated bisphenol A di(meth)acrylate monomer without reactivediluent.

The present invention is generally directed to a low viscosity, curablecasting resin composition for producing articles having a highrefractive index, high impact strength and inherent UV protection. Thecasting resin compositions are radiation and/or thermally curable. Morepreferably, the casting resin compositions of this invention are UVradiation curable.

In one embodiment, the high refractive index curable compositioncomprises a core resin mixture comprising:

(i) an ethoxylated bisphenol A di(meth)acrylate having the formula (I):

wherein n and n′ independently are 0-30, R₁-R₄ independently represent Hor C₁-C₆ alkyl, X is O, S, SO₂, CO₂, CH₂, CH═CH, C(CH₃)₂ or a singlebond, and y₁-y₈ independently represent H, OH, halogen, mercaptan orC₁-C₄ alkyl,

(ii) an ethoxylated bisphenol A di(meth)acrylate having the formula(II):

wherein m and m′ independently are 1-30, R-R₄ independently represent Hor C₁-C₆ alkyl, X is O, S, SO₂, CO₂, CH₂, CH═CH, C(CH₃)₂ or a singlebond, and y₁-y₈, independently represent H, OH, halogen, mercaptan orC₁-C₄ alkyl, and

(iii) a reactive diluent;

the mixture having greater than 70 parts by weight of the composition ofthe combined components (i) and (ii), and less than 30 parts by weightof the composition of component (iii), based on the total parts byweight of the core resin equaling 100, and n and n′ being less than mand m so as to provide a refractive index of greater than 1.53 and ahigh impact resistance after curing the composition.

The di(meth)acrylates of formulae I and II may preferably be present at72 parts, more preferably 75 parts, even more preferably at 77 parts,and most preferably at 80 parts by weight of the composition of combinedcomponents (i) and (ii).

In formula I: n and n′ preferably are 0-15, more preferably 0-8, andeven more preferably 0-4; one or both of R₂ and R₄ preferably representH or CH₃, and more preferably CH₃; one or both of R₂ and R₃ preferablyrepresent H; X preferably represents C(CH₃)₂; and/or one or more ofy₁-y₈ preferably represent H.

In formula II m and m′ preferably are 1-15, more preferably 3-12, andeven more preferably 5-8; one or both of R₁ and R₄ preferably representH or CH₃, and more preferably CH₃; one or both of R₂ and R₃ preferablyrepresent H; X preferably represents C(CH₃)₂; and/or one or more ofy₁-y₈ preferably represent H.

The degree of alkoxylation in formulae I and II can generally be variedto give the high refractive index and superior impact resistance of theinvention throughout the scope of compounds covered by the genericstructure for formulae I and II. The impact resistance of the curedcompositions of this invention may, of course, vary. The resinpreferably gives a composition upon polymerization and curing thatpasses the FDA required drop ball #1 impact resistance test, morepreferably passes the drop ball #10 test, and even more preferablypasses the drop ball #13 test. High impact resistance, for purposes ofdefining the cured compositions of this invention, means at leastpassing the drop ball #1 impact resistance test. One is able, bybalancing the alkoxylation in formulae I and II, to obtain a finalcomposition from many combinations of formulae I and II that satisfiesthe physical properties of the inventive compositions.

In a second embodiment, the high refractive index curable compositioncomprises a core resin mixture comprising:

(i) an ethoxylated bisphenol A di(meth)acrylate having the formula (I):

wherein n and n′ independently are 0-4, R₁ and R₄ independentlyrepresent H or CH₃, R₂ and R₃ are H, X is C(CH₃)₂, and y₁-y₈ are H,

(ii) an ethoxylated bisphenol A di(meth)acrylate having the formula(II):

wherein m and m′ independently are at least 5, R₁ and R₄ independentlyrepresent H or CH₃, R₂ and R₃ are H, X is C(CH₃)₂, and y₁-y₈ are H, and

(iii) a reactive diluent;

the mixture having greater than 70 parts by weight of the composition ofthe combined components (i) and (ii), and less than 30 parts by weightof the composition of component (iii), based on the total parts byweight of the core resin equaling 100.

In the first and second embodiments, the curable composition preferablycomprises a core resin mixture wherein (a) component (i) comprises atleast 5 parts by weight of the composition of (1) the ethoxylatedbisphenol A di(meth)acrylate of formula (I) or (2) a mixture ofethoxylated bisphenol A di(meth)acrylates of formula (I), and n and n′independently are 0-4, and (b) component (ii) comprises 10-75 parts byweight of the composition of (1) the ethoxylated bisphenol Adi(meth)acrylate of formula (II) or (2) a mixture of ethoxylatedbisphenol A di(meth)acrylates of formula (II), and m and m′independently are at least 5.

Preferably, the curable composition of these embodiments comprises acore resin mixture wherein (a) component (i) comprises at least 30 partsby weight of the composition of the ethoxylated bisphenol Adi(meth)acrylate of formula (I), and n and n′ are 1, and (b) component(ii) comprises 10 to 55 parts by weight of the composition of a mixtureof ethoxylated bisphenol A di(meth)acrylates of formula (II), in which mand ml independently are 6 and 15.

More preferably, the curable composition of these embodiments comprisesa core resin mixture wherein (a) component (i) comprises at least 30parts by weight of the composition of the ethoxylated bisphenol Adi(meth)acrylate of formula (I), and n and n are 1, and (b) component(ii) comprises 20-65 parts by weight of the composition of theethoxylated bisphenol A di(meth)acrylate of formula (II), and m and m′are 6.

In a third embodiment, the high refractive index curable compositioncomprises

(a) a core resin comprising

(i) greater than 70 parts by weight of the composition of an ethoxylatedbisphenol A di(meth)acrylate or a mixture of ethoxylated bisphenol Adi(meth)acrylates having the formula (I):

wherein n and n′ independently are 0-30, R₁-R₄ independently represent Hor C₁-C₆ alkyl, X is O, S, SO₂, CO₂, CH₂, CH═CH, C(CH₃)₂ or a singlebond, and y₁-y₈ independently represent H, OH, halogen, mercaptan orC₁-C₄ akyl,

(ii) less than 30 parts by weight of the composition of a reactivediluent, based on the total parts by weight of the core resin equaling100; and

(b) up to 2 parts by weight of a UV absorber per 100 parts by weight ofthe core resin.

The high index curable composition of this invention having a core resin(component (a)) and a UV absorber (component (b)) therein preferablycomprises a core resin (component (a)) comprising from about 75 to about85 parts by weight of the ethoxylated bisphenol A di(meth)acrylate offormula (I) (component (i)) and from about 15 to about 25 parts byweight of the reactive diluent (component (ii)), based on the totalparts by weight of the core resin equaling 100.

In the third embodiment, component (i) of the core resin preferablycomprises at least 5 parts by weight of the core resin of (1) theethoxylated bisphenol A di(meth)acrylate of formula (I), and n and nindependently are 0-2 or (2) a mixture of ethoxylated bisphenol Adi(meth)acrylates of formula (I), and n and n′ independently are 0-2,and 10-75 parts by weight of the core resin of (1) the ethoxylatedbisphenol A di(meth)acrylate of formula (I), and n and n′ independentlyare 3-15 or (2) a mixture of ethoxylated bisphenol A di(meth)acrylatesof formula (I), and n and n′ independently are 3-15.

More preferred for this third embodiment, component (i) of the coreresin comprises at least 30 parts by weight of the core resin of theethoxylated bisphenol A di(meth)acrylate of formula (I), and n and n′are 1, and 20-65 parts by weight of the composition of (1) thecthoxylated bisphenol A di(meth)acrylate of formula (I) wherein n and nindependently are 3-15 or (2) a mixture of ethoxylated bisphenol Adi(meth)acrylates of formula (I), and n and n′ independently are 3-15.

Further, the high index curable resin compositions of this invention mayinclude additional components such as thermal or UV initiators or otherknown additives such as light stabilizers. Moreover, the high indexresin compositions are preferably UV curable.

All of the embodiments described above are low viscosity curable resincompositions which may be used to produce lenses having a refractiveindex of at least 1.53, and preferably of at least 1.56. The cured resincompositions have excellent impact strength even with lenses having 1 mmcenter thickness. In addition, the cured resin compositions have an Abbevalue of 38. In addition to the superior properties above, theembodiment of the high index curable composition having a UV absorbertherein has at least 95%, preferably at least 99% inherent UVAprotection up to 380 nm and 100% inherent UVB protection.

The methacrylate monomer of ethoxylated bisphenol A di(meth)acrylate ispreferred over the acrylate monomer. In formulae (I) and (II), as thenumber (n, n′, m and/or m′) of ethylene oxide units increases, theimpact strength increases; however, the refractive index decreases. Itis preferred, therefore, that the proper balance of ethoxylatedbisphenol A di(meth)acrylates of formulae (I) and (II) having differentdegrees of ethoxylation be achieved.

The core resin preferably comprises less than 30 parts by weight ofreactive diluent, preferably a higher refractive index (RI>1.51)reactive diluent. Preferably, the core resin comprises 5-20 parts byweight of reactive diluent per hundred parts core resin. High refractiveindex reactive diluents are preferably introduced to raise the overallrefractive index and to adjust the overall properties of the castingresin composition.

The reactive diluents useful in the high index casting resincompositions of this invention include 1,6-hexanediol di(meth)acrylate,trimethylolpropane tri(meth)acrylate, tri(meth)acrylate, isobornyl(meth)acrylate, vinyl benzoate, vinyl 4-t-butyl benzoate, styrene,divinyl benzene and mixtures thereof. The more preferred reactivediluents are vinyl benzoate, vinyl t-butyl benzoate, styrene, andmixtures thereof. The most preferred reactive diluent for thiscomposition is styrene.

UV absorbers can be used to impart inherent UV protection to the highindex curable casting resin compositions of this invention. The highrefractive index composition of this invention preferably comprises upto 2 parts by weight of UV absorber per 100 weight parts of the coreresin composition. More preferably, the composition comprises up to 0.5parts by weight of UV absorber per 100 weight parts of the core resin.Preferred UV absorbers are benzotrizole derivatives, including but notlimited to TINUVIN 328, TINUVIN 384, TINUVIN 900, TINUVIN 1130 andTINUVIN 400, manufactured by Ciba-Geigy of Hawthorne, N.Y. TINUVIN 328is the more preferred UV absorber. Chemically, TINUVIN 328 is 2-(3′,5′-bis(1,1-dimethylpropyl)-2′-hydroxyphenyl)-2H-benzotriazole.

Up to 2 parts by weight of a UV initiator per 100 parts by weight ofcore resin may be used in the composition. Preferably, 0.1-1.5 parts byweight of UV initiator is used based on the weight of the core resin. UVinitiators which are useful in the composition include, but are notlimited to, benzophenone, 2,2-dimethoxy-2-phenyl acetophenone,1-hydroxycyclohexyl phenyl ketone,2-methyl-1-[4-(methylthio)phenyl]-2-morpholino propan-1-one,2-hydroxy-2-methyl-1-phenyl-propan- 1 -one,bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentyl phosphine oxide,2,4,6-trimethylbenzoyl diphenylphosphine oxide,bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide and mixtures thereof.

Preferred UV initiators include, but are not limited to,2,4,6-trimethylbenzoyl diphenylphosphine oxide,2-hydroxy-2-methyl-1-phenyl-propan-1-one and 1-hydroxycyclohexyl phenylketone and mixtures thereof. A more preferred UV initiator comprises themixture of 2,4,6-trimethylbenzoyl diphenylphosphine oxide and2-hydroxy-2-methyl-1-phenyl-propan-1-one, most preferably by the weightratio of 1/9-9/1.

The initiator in the composition may also be a mixture of UV and thermalinitiators. Thermal initiators which are useful in the compositioninclude, but are not limited to, t-amyl peroxy-2-ethylhexanoate,t-butylperoxy-2-ethylhexanoate, t-butyl peroxyl-2-methylbenzoate,1,1-di-(t-butylperoxy)-3,3,5-trimethylcyclohexane, t-butylperoxy-3,5,5-trimethylhexanoate, t-butylperoxy 2-ethylhexyl carbonate,dibenzoyl peroxide, t-amyl peroxybenzoate and mixtures thereof.

Preferred thermal initiators include, but are not limited to, t-amylperoxy-2-ethylhexanoate, t-butyl peroxy-2-ethylhexanoate, t-butylperoxy-3,5,5-trimethylhexanoate and mixtures thereof. In one particularembodiment, the composition comprises 0.1-1.5 and 0.01-1.0 parts, andmore preferably, 0.1-1.0 and 0.01-0.5 parts by weight of a mixture of UVand thermal initiators, per 100 parts by weight of the core resin,respectively.

A light stabilizer may be present in the composition of this invention.Preferably, up to 1.0 part by weight of a light stabilizer per 100 partsby weight of the core resin may be used. Preferred light stabilizersinclude, but are not limited to, TINUVIN 123, TINUVIN 292 AND TINUVIN144, also manufactured by Ciba-Geigy Corp. of Hawthorne, N.Y. The mostpreferred light stabilizer isbis(1,2,2,6,6-pentamethyl-4-piperidinyl)sebacate. They do not act byabsorbing UV light, but rather by scavenging free radicals. The UVabsorber also acts as a light stabilizer to slow down the degradationcaused by UV radiation.

Some advantageous features of preferred compositions of the presentinvention are:

1. The viscosity of compositions is very low so that it can be easilyprocessed in the filling stage;

2. The compositions can be cured in 5 min. or less with UV exposure;

3. The cured lens substrates having a UV absorber therein provide atleast 99% inherent UVA up to 380 nm and 100% UVB blockage so that nosecondary UV treatment and its related processes are required; and/or

4. The cured lenses exhibit a refractive index of 1.56, excellent impactresistance even with Imm center thickness, and very goodthermomechanical properties.

The viscosity of the compositions of this invention is preferably lessthan 1000 cps, and more preferably is less than 400 cps, at ambienttemperature (22°-24° C.).

The additives for the compositions of this invention preferably comprisea UV absorber for promoting UV protection and/or a stabilizer for longterm stability of the cured materials. Preferably, the compositioncomprises up to 2 parts by weight of a UV absorber per 100 parts byweight of the core resin and up to a total of 3 parts by weight ofcombined initiators per 100 parts by weight of the core resin. Theinitiators may be UV and/or thermal.

Having inherent UV protection in the cured lenses of the presentinvention eliminates the need for typical UV tinting and related processsteps. As such, the lens manufacture cycle time and the cost ofmanufacture can be dramatically reduced.

In a further aspect of the present invention, a polymeric article isformed from a composition as described above. The polymeric article maybe a lens or other optical article. The optical article may providecharacteristics equal to or greater than those achievable with articlesmade from previously known formulations, but with a considerably reducedcure time, substantially increased throughput, excellent impactresistance and inherent UV protection. The optical article may befurther characterized by having an increased refractive index withoutdegrading other important lens physical properties such as density,impact resistance, color and rigidity (hardness and heat resistance).

The overall refractive index of optical articles produced from thecompositions of the present invention are preferably from approximately1.53 to 1.57, more preferably 1.55 to 1.56. The optical articlesproduced from the compositions of this invention include, but are notlimited to lenses, prisms and video disks.

An article is produced according to this invention by processing andcuring a composition of this invention. In one embodiment, a glass moldis filled with a composition as described herein and the composition isexposed to a radiation source while in the mold to cure the compositionand form a cured article. The cured article is removed from the mold andthe cured article is annealed. Preferably, the article is a lens.Preferably, the radiation source provides UV radiation for curing thecomposition. The radiation source may be a grid, mercury, xenon or anyother appropriate actinic radiation source.

EXAMPLES

The following examples are put forth so as to provide those of ordinaryskill in the art with a more complete disclosure and description of howthe resin compositions claimed herein are made and evaluated. They arenot intended to limit the scope of what the inventors regard as theirinvention. Efforts have been made to insure accuracy with respect tonumbers (e.g., amounts, temperature, etc.) but some errors anddeviations should be accounted for. Unless indicated otherwise, partsare by weight, temperature is in ° C. or is at room temperature andpressure is at or near atmospheric.

Viscosity was measured by Brookfield viscometer at ambient temperature(22-24° C.).

The FDA requires that the impact resistance of ophthalmic lenses conformto certain requirements as defined by the steel drop ball tests of theAmerican National Standards Institute, Inc. (ANSI). The ANSI Z80.1—1979(Revision of ANSI Z80.1—1972 approved Nov. 21, 1978) outlines theAmerican National Standard Recommendations for impact resistance (steeldrop ball test) for prescription ophthalmic lenses in section 4.8.According to ANSI Z80.1—1979, section 4.8.4, the impact resistance ofophthalmic lenses subject to individual tests is measured with a 15.00mm (⅝ inch =0.625 inch) diameter steel ball weighing not less than 16grams dropped from a height of not less than 127 cm. (50 inches), or anequivalent impact. Steel balls must comply with the requirements of ANSIspecifications for metal balls, ANSI/AFBMA Std 10-1975, or the latestrevision thereof, for chrome alloy steel (AISI Type E52100), of density27.5 balls per pound, ball grade No. 25 or better.

The impact resistance of lenses resulting from the compositions of thisinvention was measured by dropping a series of steel balls (thespecification for which is indicated in Table 1 below) from 50 inchesuntil the sample was broken. The largest ball size that did not breakthe sample was recorded. The FDA requirement for ophthalmic lenses ispassing the drop ball #1 test outlined in Table 1. The average drop ballvalue out of at least four flat samples having 2 mm thickness wasrecorded in Tables 2 and 3.

TABLE 1 Steel ball specification Drop ball Diameter (inch) Mass (g) 1 ⅝16.02 2 {fraction (11/16)} 21.33 3 ¾ 27.84 4 {fraction (13/16)} 35.55 5⅞ 44.02 6 {fraction (15/16)} 54.43 7 1 66.00 8 1{fraction (1/16)} 78.879 1⅛ 95.18 10 1{fraction (3/16)} 112.01 11 1¼ 128.78 12 1{fraction(5/16)} 151.05 13 1⅝ 173.30 14 1{fraction (7/16)} 198.60 15 1½ 225.55

Refractive index (RI ) and Abbe value were measured by a refractometerat room temperature (22°-24°).

Shore D hardness was measured by a Durometer (type D). This is themeasurement of sample hardness.

Flex modulus was measured by Instron according to ASTM D790 to monitorstiffness of a material.

Heat distortion temperature (HDT) was characterized by TMA with a microthree point bending set up according to ASTM D648 at the rate of 5°C./min and was reported as the onset temperature.

Glass transition temperature (Tg) was also measured by TMA at the rateof 5° C./min and was reported as the onset temperature.

UV transmission was measured by UV/VIS spectrometer.

Density was measured by an Ultrapycnometer.

Examples 1-3

Table 2 illustrates three examples of low viscosity casting formulationsbased on ethoxylated bisphenol A dimethacrylate (EBADMA) derivatives andhigh index reactive diluents. Physical properties of each formulationare also provided.

The formulations of examples 1-3 were mixed with 0.5 parts by weight ofUV initiators, based on 100 parts by weight of the core resin. The UVinitiators were 2-hydroxy-2-methyl-1-phenyl-propan-1-one and2,4,6-trimethylbenzoyl diphenylphosphine oxide at the weight ratio of20/1. The resulting resins were filled between two glass plates andcured into flat samples with 2 mm thickness under a Fusion System F300lamp (3 passes each side under at 2.5 ft/min) without annealing.Examples 1 and 2 show the relationship between impact resistance andlength of the ethylene oxide units (n) in EBADMA. A comparison ofexamples 1 and 3 in Table 2 indicates that styrene as a reactive diluentlikely raises the refractive index more than vinyl benzoate.

TABLE 2 Formulations and physical properties of Examples 1-3Formulations in Parts by Weight Based on 100 Total Parts PhysicalProperties EBADMA EBADMA EBADMA EBADMA Vinyl Viscosity Impact RefractiveShore D Example (n = 1) (n = 15) (n = 6) (n = 3) benzoate Styrene (cps)resistance index hardness 1 50 20 10 20 205 5 1.556 80 2 50 20 10 20 2053 1.557 81 3 53 20 10 17 220 5 1.561 81

Examples 4 and 5

Table 3 shows two additional examples. The formulations of examples 4and 5 included EBADMA derivatives and styrene as the reactive diluent.The formulations also included additives. The additives were UVinitiators, a thermal initiator, and a UV absorber. Specifically, 0.75parts by weight of UV initiators, based on 100 parts by weight of coreresin, consisting of 2-hydroxy-2-methyl-1-phenyl-propan-1-one and2,4,6-trimethylbenzoyl diphenylphosphine oxide at the weight ratio of1/1 were used. Further, 0.0125 parts by weight, based on 100 parts byweight of core resin, of t-butyl peroxy-3,5,5-trimethylhexanoate as athermal initiator and 0.06 parts by weight, based on 100 parts by weightof core resin, of TINUVIN 328 as a UV absorber were used. The mixedresin was filled in the mold cavity and subjected to a low pressuremercury lamp (351 nm, 5 mm/cm²) for 5 min from both sides, followed byan annealing process for 25 minutes at 249° F. in a conveyer oven.

TABLE 3 Formulations and physical properties of Examples 4 and 5Formulations in Parts by Weight Based on 100 Total Parts PhysicalProperties Ex- EBADMA EBADMA EBADMA Viscosity Impact Refractive Shore DModulus T% (315- Density ample (n = 1) (n = 15) (n = 6) Styrene (cps)resistance index hardness Tg HDT (kpsi) 380 nm) (g/cc) 4 53 20 10 17 220 7 1.561 81 >74 >65 286 <1% 1.18 5 33 50 17 200 13* 1.560 81 >74 >65 315<1% 1.16 *Similar impact resistance was also observed on lenses with 1mm center thickness

The significant difference between examples 4 and 5 is the impactresistance. The impact resistance of example 5 is much higher than thatof example 4. This demonstrates that the balance of the degree ofethoxylation (n) of the EBADMA derivatives in the formulation plays animportant role in determining the impact resistance of the curedsamples. For instance, incorporation of EBADMA where n=15 does notnecessarily provide better impact resistance even though it has a higherdegree of ethoxylation. Process conditions and additives also affect thefinal physical properties (compared with examples 3 with 4). Lenses with1 mm center thickness made from example 5 also show similar impactresistance to that of flat samples. The Abbe value measured 38 at 25° C.

Throughout this application, where publications are referenced, thedisclosures of these publications in their entireties are herebyincorporated by reference into this application in order to more fullydescribe the state of the art to which this invention pertains.

Finally, it is to be understood that various other modifications and/oralterations may be made without departing from the spirit of the presentinvention as outlined herein.

What is claimed is:
 1. A high refractive index composition consistingessentially of: a core resin mixture comprising (i) a first compoundhaving the formula (I):

wherein n is from 0-30, R₁-R₄ independently represent H or C₁-C₆ alkyl,X is O, S, SO₂, CO₂, CH₂, CH═CH, C(CH₃)₂ or a single bond, and y₁-y₈independently represent H, OH, halogen, mercaptan or C₁-C₄ alkyl, (ii) asecond compound having the formula (II):

wherein m is from 1-30, R₁-R₄ independently represent H or C₁-C₆ alkyl,X is O, S, SO₂, CO₂, CH₂, CH═CH, C(CH₃)₂ or a single bond, and y₁-y₈independently represent H, OH, halogen, mercaptan or C₁-C₄ alkyl, and(iii) a reactive diluent comprising 1,6-hexanediol di(meth)acrylate,trimethylolpropane tri(meth)acrylate, isobomyl (meth)acrylate vinylbenzoate, vinyl 4-t-butyl benzoate, styrene, divinyl benzene or amixture thereof, the mixture having greater than 70 parts by weight ofthe composition of the combined components (i) and (ii), and less than30 parts by weight of the composition of component (iii), based on thetotal parts by weight of the core resin equaling 100, and n is less thanm so as provide a refractive index of greater than 1.53 and a highimpact resistance after curing the composition.
 2. The composition ofclaim 1 wherein (a) component (i) comprises at least 5 parts by weightof the composition of (1) the first compound or (2) a mixture of two ormore first compounds, and n is from 0-4; and (b) component (ii)comprises 10-75 parts by weight of the composition of (1) the secondcompound or (2) a mixture of two or more second compounds, and m foreach second compound is at least
 5. 3. The composition of claim 1,wherein (a) component (i) comprises at least 30 parts by weight of thecomposition of the first compound, and n is 1, and (b) component (ii)comprises 20-65 parts by weight of the composition of the secondcompound, and m is
 5. 4. The composition of claim 1, wherein (a)component (i) comprises at least 30 parts by weight of the compositionof the first compound, and n is 1, and (b) component (ii) comprises 10to 55 parts by weight of the composition of a mixture comprising twosecond compounds, wherein the value of m for one of the second compoundsis 6, and the value of m for the other second compound is
 15. 5. Thecomposition of claim 1, wherein R₁ and R₄ are CH₃.
 6. The highrefractive index composition of claim 1 wherein, in formula (I), n isfrom 0-4, R₁ and R₄ independently represent H or CH₃, R₂ and R₃ are H, Xis C(CH₃)₂, and y₁-y₈ are H; and in formula (II), m is at least 5, R₁and R₄ independently represent H or CH₃, R₂ and R₃ are H, X is C(CH₃)₂,and y₁-y₈ are H.
 7. The composition of claim 1, comprising 5-20 parts byweight of a reactive diluent, based on the total parts by weight of thecore resin equaling
 100. 8. The composition of claim 1, wherein thereactive diluent has a refractive index of 1.51 or higher.
 9. Thecomposition of claim 1, wherein the reactive diluent is styrene.
 10. Thecomposition of claim 1, wherein the composition is radiation curable.11. The composition of claim 1, wherein the composition is ultravioletradiation curable.
 12. The composition of claim 1, wherein thecomposition is thermally curable.
 13. The composition of claim 1,further comprising 0.01-2.0 parts by weight of the composition of aultraviolet initiator per 100 parts by weight of the core resin.
 14. Thecomposition of claim 13, wherein the UV initiator is selected from thegroup consisting of benzophenone, 2,2-dimethoxy-2-phenyl acetophenone,1-hydroxycyclohexyl phenyl ketone,2-methyl-1-[4-(methylthio)phenyl]-2-morpholino propan-1-one,2-hydroxy-2-methyl-1-phenyl-propan-1-one,bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentyl phosphine oxide,2,4,6-trimethylbenzoyl diphenylphosphine oxide,bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide and mixtures thereof.15. The composition of claim 13, wherein the UV initiator comprises amixture of 2,4,6-trimethylbenzoyl diphenylphosphine oxide and2-hydroxy-2-methyl-1-phenyl-propan-1-one.
 16. The composition of claim13, wherein the UV initiator is a mixture of 2,4,6-trimethylbenzoyldiphenylphosphine oxide and 2-hydroxy-2-methyl-1-phenyl-propan-1-one ina weight ratio of 1/9-9/1.
 17. The composition of claim 1, furthercomprising up to 1.0 part by weight of thermal initiator per 100 partsby weight of the core resin.
 18. The composition of claim 17, whereinthe thermal initiator is selected from the group consisting of t-amylperoxy-2-ethylhexanoate, t-butyl peroxy-2-ethylhexanoate, t-butylperoxyl-2-methylbenzoate,1,1-di-(t-butylperoxy)-3,3,5-trimethylcyclohexane, t-butylperoxy-3,5,5-trimethylhexanoate, t-butyl peroxy 2-ethylhexyl carbonate,dibenzoyl peroxide, t-amyl peroxy benzoate and mixtures thereof.
 19. Thecomposition of claim 17, wherein the thermal initiator is t-amylperoxy-2-ethylhexanoate, t-butyl peroxy-2-ethylhexanoate, t-butylperoxy-3,5,5-trimethylhexanoate or a mixture thereof.
 20. Thecomposition of claim 1, further comprising a mixture of a ultravioletinitiator and a thermal initiator.
 21. The composition of claim 1,further comprising up to 0.5 parts by weight of a ultraviolet absorberper 100 parts by weight of the core resin.
 22. The composition of claim21, wherein the UV absorber is2-(3′,5′-bis(1,1-dimethylpropyl)-2′-hydroxyphenyl)-2H-benzotriazole. 23.The composition of claim 21, having an inherent 100% ultraviolet Bprotection and at least 95% ultraviolet A protection up to 380 nm at thethickness of 1 mm.
 24. The composition of claim 21, having an inherentUV protection of greater than 99% up to 380 nm at the thickness of 1 mm.25. The composition of claim 1, further comprising up to 1 part byweight of a light stabilizer per 100 parts by weight of the core resin.26. The composition of claim 25, wherein the light stabilizer isbis(1,2,2,6,6, -pentamethyl-4-piperidinyl)sebacatc.
 27. The compositionof claim 1, having a viscosity of less than 1000 cps at roomtemperature.
 28. The composition of claim 1, having a viscosity lessthan 400 cps at room temperature.
 29. The composition of claim 1, havingan impact resistance that passes the Food and Drug Administrationrequirement with lenses of 1.0 mm center thickness after curing.
 30. Anarticle made from the composition of claim
 1. 31. The article of claim30, in the form of a lens or other optical element.
 32. A highrefractive index composition consisting essentially of: (a) a coreresine comprising great than 70 parts by weight of the composition of afirst compound or a mixture comprising two or more first compounds,wherein the first compound has the formula (I):

wherein n is from 0-30, R₁-R₄ independently represent H or C₁-C₆ alkyl,X is O, S, SO₂, CO₂, CH₂, CH═CH, C(CH₃)₂ or a single bond, and y₁-y₈independently represent H, OH, halogen, mercaptan or C₁-C₄ alkyl, (ii)less than 30 parts by weight of the composition of a reactive diluentcomprising 1,6-hexanedi ol di(meth)acrylate, trimethylolpropanetri(meth)acrylate, isobornyl (meth)acrylate, vinyl benzoate, vinyl4-t-butyl benzoate, styrene, divinyl benzene or a mixture thereof, basedon the total parts by weight of the core resin equaling 100; and (b) upto 2 parts by weight of an ultraviolet absorber per 100 parts by weightof the core resin.
 33. An article made from the composition of claim 32.34. The article of claim 33, in the form of a lens or other opticalelement.
 35. A method of forming a cured article comprising the stepsof: (a) filling a mold with the composition as defined in claims 1, 6 or32, (b) curing the composition of step (a) by exposure to a radiationsource thereby forming a cured article; (c) demolding the cured article;and (d) annealing the cured article.
 36. The method of claim 35, whereinthe article is a lens.
 37. The method of claim 35, wherein the mold isfilled by injection through a gasket.
 38. The method of claim 35,wherein step (b) is effected in 15 minutes or less.
 39. The method ofclaim 35, wherein the radiation source provides UV radiation for curingthe composition.
 40. The method of claim 35, wherein the radiationsource is a grid, mercury, xenon, or other actinic light source.
 41. Themethod of claim 35, wherein step (d) is effected in 15-30 minutes at atemperature of from 150 to 300° F.